Polarized signal-bell



(No Model.)

F. R. MQBERTY. POLARLZLD SIGNAL BELL.

Patented Feb. 1, 1898.

Berl;

UNITED STATES PATENT OEEiCE.

FRANK R. MCBERTY, OF DOWNERS GROVE, ILLINOIS, ASSIGNOR TO THE TESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS.

POLARlZED SIG NAL-BELL.

SPECIFICATION forming part of Letters Patent No. 598,269, dated February 1, 1898.

Application iiled November 24, 1896. Serial Nol 613,262. @lo model.)

To @ZZ whom, t may concern.-

Be it known that I, FRANK R. MGBERTY, a citizen of the United States, residing at Downers Grove, in the county of Du Page and State of Illinois, have invented a certain new and useful Improvement in Polarized Signal-Bells, (Case No. 48,) of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specifcation.

My invention is a signal-bell for telephone substations, and is designed to be responsive only to alternating orpulsating signaling-currents and to remain inert when traversed by an unvarying current. It is intended for use in telephone-lines furnished with storage batteries at their substations and with means for charging the storage batteries over the lineeireuits during the idleness of the telephones.

The operation of the bells ordinarily employed in telephone-substations is seriously interfered with by this charging-current constantly present in the line.

My improvement consists in surrounding the armature or movable portion of the bell by a coil connected with the line-circuit and acting on the armature in opposition to the windings of the electromagnet of the bell,and also with a closed conductingQcircuit of low resistance in position to protect the armature from magnetization by the said coil when it is traversed by the rapidly-varying currents. This closed conducting-circuit may be a copper tube placed about the armature and forming the spool on which the before-mentioned coil is wound. Then the various windings of the bell are traversed by an unvaryin g current, the effect of the electromagnet-of the bell upon the armature is neutralized by the opposing effect of the helix about the armature. When, however, the current through these windings is rapidly varied, the magnetization of the magnet is correspondingly varied, while that of the armature remains practically constant, being unaffected by the varying field of the wiudin g about it, so that the armature is thrown into vibration in the This improved bell is illustrated in the accompanying drawings, of which-- Figure 1 is a front elevation of the instrument. Fig. 2 is a side elevation thereof,and Fig. is a transverse sectional view. Fig. 4 is a diagram representing the circuits through the different windings iu conjunction with a telephone-line, a local storage battery at the substation thereof, and a central chargingbattery therefor.

The bell comprises the usual electromagnet d, a centrally-pivoted armature b before its poles, and a permanent magnet c, with one pole presented to the yoke of the magnet a and its other extended into position to polarize the armature l). In the present invention the armature b is surrounded by a heavy spool or tube d of copper,over which is wound a coil e of insulated wire. The different parts may be assembled in a frame in the usual way. The armature l) carries a tongue f, provided with a hammer which vibrates between two gongs g.

The windings a a2 of the magnet a and the winding e about the armatureb are connected in series in the line-circuit, the polarity of winding e being arranged to oppose that of the windings a/ a2. The winding e should have a sufficient number of turns to completely neutralize the effect of magnet a upon the armature. In Fig. 4t this appliance is shown connected in a circuit with a charging-battery 7L, which may be located at a central office, and a local storage batteryft' at the substation. The magnet of a signalcontrol ling instrumentis connected in the telephoneline, and a spring-jack is connected with the line for the purpose of uniting it with other lines. A calling-plug 71;, arranged for insertion into the spring-jack, forms the terminal of a generator of alternating current.

lVhile the constant current from the battery h iiows through the windings of the bell the armature of the bell remains in a neutral condition and stands indifferently in contact with either pole of the magnet a.

ever, the generator of alternating current is connected with the line by means of the plug, the rapid undulations of the current produced thereby in the circuit cause rapid variations 9 Vhen, howor alternations in the magnetism of magnet c. The iield of winding e is of course of similar Varying character; but the energy of this latter varyin g lield is expended in inducing currents in the copper spool d, so that the armature b remains unaffected by it. Hence the armature, polarized by the permanent magnet, is thrown into Vibration by the varying magnetism of magnet c in the usual manner.

The use of my invention is of course not limited to signal-bells, but may be applied in any case where it is desired to render an armature inert as to continuous currents in its magnet, but responsive to Varying or alterous currents in its windings, but it remains responsive to Varying currents, as described.

2. The combination with an electromagnet, its armature and the circuit including the magnet-windings, of a closed conducting-circuit of low resistance surrounding the armature, and a winding connected with the said circuit surrounding the said closed conducting-circuit and adapted to neutralize the magnetic effect of the magnet upon the armature, substantially as described.

3. The combination with a polarized magnet and a centrally-pivoted armature therefor, of a tube of copper surrounding the armature, and a helix surrounding the tube of copper, the said helix being connected with the circuit of the magnet and being adapted to neutralize the magnetic effect thereof on the armature, substantially as described.

4. The combination with a telephone-line, a source of continuous current therein, a source of alternating callingcurrent and means for connecting it with the line, of a signaling instrument in the line comprising a magnet and an armature therefor, a signal actuated by the armature, the magnet having differential windings connected with the line-circuit to neutralize each other, and a closed conducting-circuit interposed between the iron of the magnetic circuit and one of said differential windings, whereby the signaling instrument remains inert as to the continuous current in the circuit, but is operated by the alternating current, as described.

In witness whereof I hereunto subscribe my name this 14th day of October, A. D. 1896.

FRANK R. MCBERTY. lVitnesses:

ELLA EDLER, DUNCAN E. WILLETT. 

